Secure chips with serial numbers

ABSTRACT

An electronic device comprising a semiconductor chip which comprises a plurality of structures formed in the semiconductor chip, wherein the semiconductor chip is a member of a set of semiconductor chips, the set of semiconductor chips comprises a plurality of subsets of semiconductor chips, and the semiconductor chip is a member of only one of the subsets. The plurality of structures of the semiconductor chip includes a set of common structures which is the same for all of the semiconductor chips of the set, and a set of non-common structures, wherein the non-common structures of the semiconductor chip of the subset is different from a non-common circuit of the semiconductor chips in every other subset. At least a first portion of the non-common structures and a first portion of the common structures form a first non-common circuit, wherein the first non-common circuit of the semiconductor chips of each subset is different from a non-common circuit of the semiconductor chips in every other subset. At least a second portion of the non-common structures is adapted to store or generate a first predetermined value which uniquely identifies the first non-common circuit, wherein the first predetermined value is readable from outside the semiconductor chip by automated reading means.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. application No. 62/385,049filed on 8 Sep. 2016, U.S. application No. 62/413,470 filed on 27 Oct.2016, U.S. application No. 62/438,548 filed on 23 Dec. 2016, U.S.application No. 62/456,144 filed on 8 Feb. 2017, U.S. application No.62/458,040 filed on 13 Feb. 2017, U.S. application No. 62/458,071 filedon 13 Feb. 2017, U.S. application No. 62/458,082 filed on 13 Feb. 2017and U.S. application No. 62/458,062 filed on 13 Feb. 2017. All priorityapplications are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The invention relates to electronic devices comprising semiconductorchips. More specifically, the invention relates to electronic devicescomprising a semiconductor chip having a common part and a unique partforming a unique circuit. The invention further relates to systems forauthentication between a plurality of remote terminals comprising suchelectronic devices and a host system based on a challenge-responseprocedure, a remote terminal for use in such system, and a method forauthentication in such system.

BACKGROUND ART

In the semiconductor industry, lithography systems are used to create,i.e. fabricate electronic devices, typically in the form of integratedcircuits formed on silicon wafer, commonly referred to as semiconductorchips. Photolithography utilizes reusable optical masks to project animage of a pattern representing the desired circuit structures onto asilicon wafer as part of the manufacturing process. The mask is usedrepeatedly to image the same circuit structures on different parts of asilicon wafer and on subsequent wafers, resulting in a series ofidentical chips being fabricated from each wafer, each chip having anidentical circuit design.

Various technologies relating to security, such as data security, securecommunications, traceability, authentication, anti-counterfeiting etc.,create an increasing need for unique chips having unique circuits orcodes, or other unique hardware features for diversification of thechips. Such unique chips are known and often implement a securityrelated operation in an obfuscated manner requiring the chip to be trulyunique. The known unique chips are typically realized after themanufacture of a chip, e.g. by manufacturing a series of identical chipsusing conventional mask-based photolithography and then, aftermanufacture, disrupting certain connections in the chip or by assessingthe uniqueness of the chip afterwards upon inspection and control ofcertain features. The masks used in this process are expensive toproduce, and manufacturing unique masks for each single chip is clearlymuch too expensive, for which reason mask based photolithography isconsidered unsuitable for fabricating unique chips.

Semiconductor chips can be created to contain predetermined data orcode, i.e. in the form of readable data, typically using mask ROM(MROM), erasable programmable read-only memory (EPROM) or electricallyerasable programmable read-only memory (EEPROM). The MROM variant usesmasked-based lithography to create the ROM including the data storedpermanently in the ROM, with the above identified drawbacks ofmask-based lithography when creating chips with unique codes. EPROM andEEPROM allow the data to be written to the ROM at a later stage, butthis disadvantageously takes control over the code away from themanufacturing process and introduces security risks.

It has been suggested to utilize maskless lithography for the purpose ofcreating unique chips. With maskless lithography no hard mask is used,and instead the required pattern representing the circuit design isinput to the maskless lithography system in the form of a design layoutdata file such as a GDSII or OASIS file containing the circuit designlayout to be transferred to the target, e.g. wafer, to be exposed by themaskless lithography system.

A maskless lithography and data input system is disclosed in WO2010/134026 in the name of Applicant of the present invention. WO2010/134026 is hereby incorporated by reference in its entirety. Thedisclosed maskless system writes patterns onto wafers directly usingcharged particle beamlets such as electron beamlets. Because the desiredpattern for exposing each chip is represented as data instead of a mask,it becomes possible to utilize such system for the manufacture of uniquechips. The pattern data that is input to the exposure system,representing the unique electronic devices or chips to be created, maybe made unique by using a different design layout data input file, e.g.a GDSII or OASIS input file, for each unique electronic device to becreated.

WO 2011/117253 and WO 2011/051301, both assigned to the Applicant of thepresent invention and hereby incorporated by reference in theirentirety, disclose various examples of electronic devices or chips thatcan be created using a charged particle lithography system.

SUMMARY OF THE INVENTION

The present invention addresses the problems of the prior art, andprovides according to an aspect of the invention an electronic devicecomprising a semiconductor chip. The semiconductor chip can comprise aplurality of structures formed in the semiconductor chip. Thesemiconductor chip can be a member of a set of semiconductor chips,where the set of semiconductor chips comprises a plurality of subsets ofsemiconductor chips, and the semiconductor chip is a member of only oneof the subsets. The subsets of the semiconductor chips may each compriseonly a single chip, so that every chip of the set is unique, or eachsubset may comprise e.g. two chips, so that each chip has a singleidentical spare. The set of semiconductor chips may consist of chips allhaving a single design for performing the same function, the chips allhaving the same input and output terminals and designed for operation inthe same system, but each subset of chips including a non-common circuitwhich is different from the circuits formed in all the other chips ofthe set. The set of semiconductor chips may comprise, for example, allthe chips formed from a single wafer.

The semiconductor chip can comprise a plurality of structures formed inthe semiconductor chip. The plurality of structures of the semiconductorchip includes a set of common structures which are the same for all ofthe semiconductor chips of the set, and a set of non-common structureswhich are the same for all of the semiconductor chips of the subset andis different from all semiconductor chips of the set which are not inthe subset. At least a first portion of the non-common structures isadapted to store or generate a first predetermined value, wherein thefirst predetermined value is readable from outside the semiconductorchip by automated reading means.

The first predetermined value is readable from outside the semiconductorchip by automated electromagnetic reading means (e.g. using anon-contact sensor), optical reading means (e.g. using an optical scanof an embedded small QR code in an upper layer of the chip), orelectronic reading means (e.g. using probe needles or by receiving anoutput signal from the chip). The first predetermined value may be, forexample, a serial number, a cryptographic key such as a public key, anaccount number, a network address such as a media access control (MAC)address or internet protocol (IP) address, or an identification code.

The first predetermined value may be readable from the structure of thesecond portion of the non-common structures, e.g. by detecting the shapeof the structures using an optical or other suitable sensor for scanningthe structures. The shape of the second portion of the non-commonstructures may be used to store the first predetermined value, e.g. byforming a metal layer in the shape of a small bar code or QR code, or anoptically identifiable set of metal lines, vias, or circuitry. Thislayer is preferably in an intermediate or lower layer, i.e. not the toplayer of the semiconductor chip, or the structures may be formed on morethan one layer.

A first non-common circuit may be formed from the first portion of thenon-common structures of the semiconductor chip and a first portion ofthe common structures of the semiconductor chip, wherein the circuitconfiguration of the first non-common circuit of the semiconductor chipsof each subset is different from a circuit configuration of any of thesemiconductor chips in every other subset.

The first non-common circuit may comprise a read-only memory circuit,which may be fabricated with the first predetermined value pre-stored inthe read-only memory circuit. The first predetermined value may bestored, for example, by the presence or absence of memory cell elementsin the read-only memory circuit, or by the connection or disconnectionof memory cell elements. Where a conventional ROM structure is used,predetermined ones of the memory cell elements (such as transistors ordiodes etc.) connecting the word lines and bit lines of the memorymatrix may be formed or not formed (or formed with varying structure) orconnected or disconnected during the chip manufacturing process, toproduce a ROM which stores the first predetermined value. In this way,the read-only memory circuit with pre-stored value may be formed duringthe manufacturing process. This type of e.g. ROM which stores thepredetermined value in its structure made during the chip manufacturingprocess, where the first predetermined value may be unique among the setof semiconductor chips, is made feasible by the use of masklesslithography.

The first non-common circuit may comprise a logic circuit which isadapted to generate the first predetermined value. The firstpredetermined value may be stored by the presence or absence ofinterconnections in the logic circuit, or the presence or absence ofcircuit elements in the logic circuit, so that the first predeterminedvalue is effectively stored in the structure of the logic circuit.

Such a memory circuit or logic circuit may comprise transistors (orother active elements) and interconnections, where the interconnectionsor the transistors (or other active elements) may be formed or notformed (or formed with varying structure) or connected, disconnected ornot connected during the chip manufacturing process, to produce a logiccircuit which generates the first predetermined value. One convenientmethod is to utilize conductive vias in the memory or logic circuit,where the vias are formed or not formed during the manufacturing processto provide a memory circuit which will store or a logic circuit whichwill generate the first predetermined value. In this way, the memory orlogic circuit may pre-store the first predetermined value during themanufacturing process.

The first predetermined value of the semiconductor chip may be differentfrom a predetermined value of every other semiconductor chip of the setof the semiconductor chips. Furthermore, the set of non-commonstructures of the semiconductor chip may be different from the set ofnon-common structures of every other semiconductor chip of the set ofthe semiconductor chips. The first non-common circuit may comprise amemory or logic circuit which is the same for all of the semiconductorchips of the subset and is different from all semiconductor chips of theset which are not in the subset, wherein the first predetermined valueuniquely identifies the first non-common circuit.

The common structures and the non-common structures of the semiconductorchip may be interconnected to form one or more electronic circuits. Theelectronic device may comprise at least one input terminal and at leastone output terminal, and the first non-common circuit may be connectedto the input and output terminals, wherein first predetermined value iselectronically readable from the output terminal. The electronic devicemay comprise at least one input terminal for receiving a challenge andat least one output terminal for outputting a response, and theelectronic circuit may form a challenge-response circuit connected tothe at least one input terminal and the at least one output terminal,wherein the challenge-response circuit is adapted for generating aresponse at the at least one output terminal based on a challengeapplied to the at least one input terminal, the challenge and theresponse having a predetermined relationship. The response generated bythe challenge-response circuit may depend on both the challenge appliedto the at least one input terminal and the first predetermined value.

The electronic device may also have a second non-common circuit formedfrom a second portion of the non-common structures of the semiconductorchip and a second portion of the common structures of the semiconductorchip. The circuit configuration of the second non-common circuit of thesemiconductor chips of each subset may be different from a circuitconfiguration of any of the semiconductor chips in every other subset.The second non-common circuit may be adapted to store or generate asecond predetermined value which is readable from outside thesemiconductor chip by automated reading means. The second non-commoncircuit may comprise a read-only memory circuit, which may be fabricatedwith the second predetermined value pre-stored in the read-only memorycircuit, similarly as described for the read-only memory circuit formedby the first non-common circuit. The second non-common circuit maycomprise a logic circuit which is adapted to generate the secondpredetermined value, similarly as described for the logic circuit formedby the first non-common circuit. The first predetermined value of thechip may have a value which uniquely identifies the second non-commoncircuit.

The plurality of structures may be formed in three or more layers of thesemiconductor chip, including one or more non-common layers containingthe non-common structures, with at least one common layer formed abovethe one or more non-common layers, wherein the at least one common layercontains common structures but no non-common structures. Optionally, allof the non-common structures may be formed on only one layer of thesemiconductor chip. The semiconductor chip may also comprise at least asecond common layer below the one or more non-common layers, the secondcommon layer containing common structures but no non-common structures.In this way, the layer(s) including the non-common structures may be‘buried’ under other layers making it more difficult to determine thestructures without expensive reverse engineering of the chip. Theplurality of structures of the electronic device may be formed in aplurality of layers of the semiconductor chip, and the non-commonstructures may include at least one of: connections between metal layersof the plurality of layers; connections between a metal layer and a gatein a contact layer of the plurality of layers; connections in a localinterconnect layer of the plurality of layers; and a P- or N-dopeddiffusion region of a transistor or diode of one of the plurality oflayers.

The non-common structures of the one or more common layers may be formedusing a maskless lithography process, such as exposure using a chargedparticle multi-beamlet lithography system or electron beam system, andthe common layers may be formed using a mask-based lithography process.The use of a maskless lithography process for forming the non-commonstructures enables forming first and second non-common circuits having avery high information storage density, much higher density than previousmethods using printed circuits, fuses, one-time programmable circuitsand memories, etc. This very high information density enables thenon-common circuits to store very long predetermined values, such asvery long cryptographic keys or many long cryptographic keys. The verysmall feature size of the non-common structures and circuits which ispossible when using maskless lithography (e.g. a feature size of lessthan 50 nm) enables the non-common circuits to be small in area and/ordistributed over multiple layers. This makes it much more difficult todiscover the data stored in the non-common circuits of the circuitlayout of the non-common circuits, either by inspection of the chip orby reverse engineering of the chip, unlike previously known techniques.Where a maskless lithography process is used to form non-commonstructures such as connections between metal layers, these may be formedby merging two conducting via to form a double via.

According to an aspect of the invention a system is proposed forauthentication between a plurality of remote terminals and a host systembased on a challenge-response procedure. Each of the remote terminalscan comprise an electronic device as described above.

According to another aspect of the invention a remote terminal isproposed adapted for use in a system described above.

According to another aspect of the invention a method is proposed forauthentication in a system described above. The method can comprisedistributing the remote terminals to a plurality of users, sending achallenge from the host system to one of the remote terminals, receivinga response from the remote terminal, and authenticating the remoteterminal if the response has to predetermined relationship with thechallenge.

The electronic device as described above may be manufactured wherein atleast a portion of the non-common structures are formed using a masklesslithographic exposure system, such as a charged particle multi-beamlithography system. At least the first portion of the common structuresmay be formed using a mask-based photolithography system and the firstportion of the non-common structures formed using a masklesslithographic exposure system.

The pattern data used to control the maskless lithographic exposuresystem may be designed to include a common chip design part that can beused in the creation of common structures and a unique or non-commonchip design part that is used in the creation of the non-commonstructures of the semiconductor chip. The unique or non-common chipdesign part can in particular be added to the pattern data just beforeexposing a target (such as a wafer) on which the semiconductor is to beformed. This may be either in the form of unique pattern data or in theform of information used to create the unique pattern data. The patterndata may be based in part on secret data provided to the masklesslithographic exposure system during creation of a unique or non-commondesign layout part. The secret data may originate from a unique datagenerator such as a black box device. These measures enable the uniqueor non-common design data to remain under control of the operator of thelithography system, and the period when the design data is exposed tooutside detection or interference is minimized, which enhances thesecurity for manufacturing unique electronic devices as described above.Another benefit is that the required design time, and processing timeand memory may remain low, because the common chip design part can bereused for the creation of multiple chips, avoiding the design andprocessing time normally required for producing unique chips.

The electronic device comprising a semiconductor chip as described aboveand in the embodiments described below, may include unique (non-common)electrical circuits to provide functions in security systems which relyon the uniqueness of the circuitry. For example, the electronic devicemay be used in a secure communication or transaction system to provideauthentication services, where the first non-common circuit of thesemiconductor chip comprises a data storage circuit such as a mask ROMwhich is fabricated with a pre-stored value and adapted to output thevalue which comprises an ID number or code uniquely identifying theelectronic device. The second non-common circuit may comprise a logic orcryptographic circuit adapted to receive an input value (e.g. achallenge input) and generate a unique output in response to the inputwhich, together with the ID, authenticates the electronic device to thesecure system.

In another example, the electronic device may be used in an equipmentmanagement system, in which the first non-common circuit is adapted asin the example above to output an ID number or code uniquely identifyingthe electronic device, and the second non-common circuit is adapted togenerate an output in response to an input to enable a function orfeature of a circuit of the electronic device, or to enable a functionor feature of software running on the electronic device or running onanother device. The second non-common circuit may be adapted to apply adecryption algorithm specific to the electronic device, or apply adecryption key specific to the electronic device, to decrypt the input,and the input may be encrypted according to the algorithm or key of thespecific chip.

In another example, the electronic device may be used in a cryptographicdata storage system, in which the first non-common circuit is adapted asin the example above to output an ID number or code uniquely identifyingthe electronic device, and the second non-common circuit is adapted toreceive data at an input and perform encryption of the received data andoutput the encrypted data, where the encryption key and/or theencryption algorithm applied by the electronic device to encrypt thedata is unique to the electronic device.

In another example, the electronic device may be used in a communicationnetwork, in which the first and/or the second non-common circuitscomprise data storage circuits fabricated with pre-stored values andadapted to output the values, such as a media access control (MAC)address or internet protocol (IP) address, which uniquely identify theelectronic device on the network. Such an electronic device may also beused in a manufacturing facility, in which the first and/or the secondnon-common circuits comprise data storage circuits fabricated withpre-stored values and adapted to output one or more values, such as anID code or cryptographic key, for uniquely matching the electronicdevice with a personalized device in which the electronic device is tobe placed (such as a smart ID chip placed in a passport or bank card ora ship with a cryptographic keys placed in personalized communicationdevice. The electronic device may be adapted to respond to a challengeto output the pre-stored value(s) and read by the machine that placesthe electronic device into the personalized device.

In another example, the electronic device may be used for securematching of a serial number(s) with cryptographic key(s). The very highinformation density of chip layer(s) written with maskless lithography,for example enabling the first non-common circuit to store a firstpredetermined value such as a serial number (which is shorter and easyto communicate and challenge) and the second non-common circuit to storea very long secret cryptographic key or many long cryptographic keys.The possibility of very large cryptographic keys allows e.g. to useone-time-pad (OTP) encryption which requires the key to be of the samelength as the message being sent, and can be impossible to break. Thevery small feature size possible when using maskless lithography alsomakes it very difficult to retrieve the cryptographic keys by inspectionor reverse engineering of the chip.

Various aspects and embodiments of the invention are further defined inthe following description and claims.

Hereinafter, embodiments of the invention will be described in furtherdetail. It should be appreciated, however, that these embodiments maynot be construed as limiting the scope of protection for the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying schematic drawings in which correspondingreference symbols indicate corresponding parts, and in which:

FIG. 1 shows a simplified unique chip and a wafer with multiple uniquechips of an exemplary embodiment of the invention;

FIG. 2 shows a simplified schematic drawing of an exemplary embodimentof a charged particle multi-beamlet lithography system;

FIG. 3 is a conceptual diagram showing an exemplary maskless lithographysystem;

FIGS. 4A-4D are schematic diagrams of exemplary embodiments of a networkarchitecture for a lithography system according to the invention;

FIG. 5 shows an exemplary functional flow diagram of an embodiment of adata path using real-line rasterization;

FIG. 6 shows a process of creating a unique chip according to anexemplary embodiment of the invention;

FIG. 7 shows a process of creating a unique chip according to anotherexemplary embodiment of the invention;

FIG. 8 shows a process of creating a unique chip according to anotherexemplary embodiment of the invention;

FIG. 9 shows a method for combining mask-based and maskless lithographyfor creating a unique chip according to another exemplary embodiment ofthe invention;

FIG. 10 shows a unique chip having a unique part including a uniquecircuit and associated unique predetermined value according to anotherexemplary embodiment of the invention;

FIG. 11 shows a unique chip having a layer storing a uniquepredetermined value according to another exemplary embodiment of theinvention; and

FIGS. 12A-D shows a conducting via formed using a conventional processand a maskless lithography process according to another exemplaryembodiment of the invention.

The figures are intended for illustrative purposes only, and do notserve as restriction of the scope or the protection as defined by theclaims.

DESCRIPTION OF EMBODIMENTS

In the following examples reference is made to ‘chips’ or ‘semiconductorchips’, referring to integrated circuits fabricated on a semiconductorwafer. However, it is to be understood that the invention is not limitedto chips and applies more generally to the creation of electronicdevices having individualized, e.g. unique features. The electronicdevice may comprise a chip or other type of electronic circuit havingone or more inputs and outputs, and functioning to store data or processan input to generate a particular output.

The process performed using charged particle multi-beamlet lithographyfor writing a pattern on a target such as a semiconductor wafer is alsoreferred to herein as an electron beam or e-beam exposure. Theseexposure methods are maskless exposure methods, where the pattern to beexposed on the target is embodied in data which is (usually) streamed tothe lithography system, rather than being embodied in a predefined mask.The charged particle/electron beams used for writing a target such as awafer during exposure are also being referred to herein as beamlets.

Individualized chips are referred to herein as ‘unique’ chips. Thisrefers to a chip which is designed and fabricated with a unique circuitstructure with respect to other chips, so that the unique chip functionsdifferently from the other chips. Such a unique chip is typically onechip of a large set of chips having the same purpose and same generalfunction, but having a slightly different circuit. For example, the setof chips may include a read only memory (ROM) having a certain datastorage capacity, each chip of the set fabricated so that it stores apredetermined data value in the ROM, where the data value is differentfor every chip of the set of chips. In another example, the set of chipsmay include a circuit for generating a predetermined output value whenprovided with a predetermined input value, where the output value isdifferent for every chip of the set of chips when provided with the sameinput value, or where each chip of the set of chips generates a uniquecombination of output value to input value.

It should be noted that it the possibility is not excluded that morethan one chip of the set of chips may have an identical design, forexample to create a spare chip for use in case the chip having the samedesign is damaged, or to create batches of the same chip for some otherreason. Thus, a set of chips may be divided into subsets, in which thechips in each subset are designed to be the same, but they are designedto be different from the chips in every other subset. A unique chip thatis designed to be different from every other chip may be referred to asa truly unique chip, i.e. the subset size is one.

The unique part of the chip, the unique structures formed as part of theunique chip, and the unique design data used for creating part of theunique chip, are also referred to herein as the non-common part,non-common structures, and non-common design data.

FIG. 1 shows an exemplary simplified diagram of a unique chip 100 formedon a semiconductor wafer 24. The unique chip 100 comprises a common part101 and a unique or non-common part 102. The common part 101 may bereplicated in other chips created on the wafer 24 resulting in multiplechips having the same identical common part 101. The unique part 102 maybe different from all of the other chips created on the wafer 24. Thisis illustrated in the top of FIG. 1 where a wafer 24 is shown containinga unique chip 100 and 39 other unique chips, each unique chip having adifferent individualized area. The combination of common part 101 andunique part 102 may result in the complete circuit for unique chip 100.

The unique part 102 may be realized by selecting and writing a uniquecombination of certain specific structures (such as interconnectinglines, conducting vias, terminals of transistors and diodes, activeregions of transistors and diodes etc.) for each chip on the wafer 24,so that each chip on the wafer has a unique structure. Chips aretypically formed from multiple layers of conducting, insulating, andsemiconducting material, and multiple exposure operations are used toform predefined structures within these layers.

Each chip on the wafer typically has conducting vias for makingelectrical connections between different conducting (metal) layers ofthe chip, as illustrated in the middle part of FIG. 1 by the black dots.Each chip on the wafer 24 may have a different combination of viasformed, by forming or not forming a via at each possible via location inthe unique part 102 of the chip, to create a different set of electricalinterconnections between layers for each chip, so that each of the chipshas an electrically-different circuit.

Each chip on the wafer typically has one or more layers ofsemiconducting material having P or N-type dopant added to form theactive regions of active circuit elements, such as transistors ordiodes, formed in the chip. Each chip on the wafer 24 may have adifferent combination of active circuit elements formed, by doping ornot-doping or varying the doping of each active circuit element in theunique part 102 of the chip, so that each of the chips has anelectrically-different circuit.

Alternatively or additionally, other connections between metal layers,connections between a metal layer and a gate e.g. in a contact layer,connections in a local interconnect layer, or other features of thecircuit may be selectively formed in a unique combination for each chipto realize the unique part 102.

The common part 101 may be created using photolithography or chargedparticle multi-beam lithography. The unique part 102 is typicallycreated using charged particle multi-beam lithography. Moreover, thepattern data used to control the beamlets in the charged particlelithography system may be designed to include a common chip design partthat is used for multiple chips on the wafer and a unique part that isused for the individualized area. For the reasons set out in thebackground section it is undesirable to generate the pattern dataincluding the common chip design part and the unique chip design part atonce. Therefore the lithography system has been adapted to enableinsertion of the unique chip design part into the pattern data at a latestage in the preprocessing stage before exposure, i.e. close to theactual patterning of the wafer. This will be explained in more detail inconjunction with FIGS. 4A-4D and FIG. 5.

FIG. 2 shows a simplified schematic drawing of an exemplary embodimentof a charged particle multi-beamlet lithography machine 1, which may beused for implementing a maskless pattern writer. Such a lithographymachine suitably comprises a beamlet generator generating a plurality ofbeamlets, a beamlet modulator patterning said beamlets into modulatedbeamlets, and a beamlet projector for projecting said beamlets onto asurface of a target. The target is for example a wafer. The beamletgenerator typically comprises a source and at least one aperture array.The beamlet modulator is typically a beamlet blanker with a blankingdeflector array and a beam stop array. The beamlet projector typicallycomprises a scanning deflector and a projection lens system.

In the embodiment shown in FIG. 2, the lithography machine 1 comprisesan electron source 3 for producing a homogeneous, expanding electronbeam 4. Beam energy is preferably maintained relatively low in the rangeof about 1 to 10 keV. To achieve this, the acceleration voltage ispreferably low, the electron source preferably kept at between about −1to −10 kV with respect to the target at ground potential, although othersettings may also be used.

The electron beam 4 from the electron source 3 may pass a doubleoctopole and subsequently a collimator lens 5 for collimating theelectron beam 4. As will be understood, the collimator lens 5 may be anytype of collimating optical system. Subsequently, the electron beam 4may impinge on a beam splitter, which is in one suitable embodiment anaperture array 6A. The aperture array 6A may block part of the beam andmay allow a plurality of subbeams 20 to pass through the aperture array6A. The aperture array preferably comprises a plate havingthrough-holes. Thus, a plurality of parallel electron subbeams 20 may beproduced.

A second aperture array 6B may create a number of beamlets 7 from eachsubbeam. Beamlets are also being referred to as e-beams. The system maygenerate a large number of beamlets 7, preferably about 10,000 to1,000,000 beamlets, although it is of course possible to use more orless beamlets. Note that other known methods may also be used togenerate collimated beamlets. This allows the manipulation of thesubbeams, which turns out to be beneficial for the system operation,particularly when increasing the number of beamlets to 5,000 or more.Such manipulation is for instance carried out by a condenser lens, acollimator, or lens structure converging the subbeams to an opticalaxis, for instance in the plane of the projection lens.

A condenser lens array 21 (or a set of condenser lens arrays) may beincluded behind the subbeam creating aperture array 6A, for focusing thesubbeams 20 towards a corresponding opening in the beam stop array 10. Asecond aperture array 6B may generate beamlets 7 from the subbeams 20.Beamlet creating aperture array 6B is preferably included in combinationwith the beamlet blanker array 9. For instance, both may be assembledtogether so as to form a subassembly. In FIG. 2, the aperture array 6Bproduces three beamlets 7 from each subbeam 20, which strike the beamstop array 10 at a corresponding opening so that the three beamlets areprojected onto the target by the projection lens system in the endmodule 22. In practice a much larger number of beamlets may be producedby aperture array 6B for each projection lens system in end module 22.In one embodiment, 49 beamlets (arranged in a 7×7 array) may begenerated from each subbeam and are directed through a single projectionlens system, although the number of beamlets per subbeam may beincreased to 200 or more.

Generating the beamlets 7 stepwise from the beam 4 through anintermediate stage of subbeams 20 has the advantage that major opticaloperations may be carried out with a relatively limited number ofsubbeams 20 and at a position relatively remote from the target. Onesuch operation is the convergence of the subbeams to a pointcorresponding to one of the projection lens systems. Preferably thedistance between the operation and the convergence point is larger thanthe distance between the convergence point and the target. Mostsuitably, use is made of electrostatic projection lenses in combinationherewith. This convergence operation enables the system to meetrequirements of reduced spot size, increased current and reduced pointspread, so as to do reliable charged particle beam lithography atadvanced nodes, particularly at nodes with a critical dimension of lessthan 90 nm.

The beamlets 7 may next pass through an array of modulators 9. Thisarray of modulators 9 may comprise a beamlet blanker array having aplurality of blankers, which are each capable of deflecting one or moreof the electron beamlets 7. The blankers may more specifically beelectrostatic deflectors provided with a first and a second electrode,the second electrode being a ground or common electrode. The beamletblanker array 9 constitutes with beam stop array 10 a modulating device.On the basis of beamlet control data, the modulating means 8 may add apattern to the electron beamlets 7. The pattern may be projected ontothe target 24 by means of components present within an end module 22.

In this embodiment, the beam stop array 10 comprises an array ofapertures for allowing beamlets to pass through. The beam stop array, inits basic form, may comprise a substrate provided with through-holes,typically round holes although other shapes may also be used. In oneembodiment, the substrate of the beam stop array 8 is formed from asilicon wafer with a regularly spaced array of through-holes, and may becoated with a surface layer of a metal to prevent surface charging. Inone embodiment, the metal may be of a type that does not form anative-oxide skin, such as CrMo.

In one embodiment, the passages of the beam stop array 10 may be alignedwith the holes in the beamlet blanker array 9. The beamlet blanker array9 and the beamlet stop array 10 typically operate together to block orlet pass the beamlets 7. If beamlet blanker array 9 deflects a beamlet,it will not pass through the corresponding aperture in beamlet stoparray 10, but instead will be blocked by the substrate of beamlet blockarray 10. But if beamlet blanker array 9 does not deflect a beamlet,then it will pass through the corresponding apertures in beamlet stoparray 10 and will then be projected as a spot on a target surface 13 ofthe target 24.

The lithography machine 1 may furthermore comprise a data path forsupplying beamlet control data, e.g. in the form of pattern bitmap data,to the beamlet blanker array 9. The beamlet control data may betransmitted using optical fibers. Modulated light beams from eachoptical fiber end may be projected on a light sensitive element on thebeamlet blanker array 9. Each light beam may hold a part of the patterndata for controlling one or more modulators coupled to the lightsensitive element.

Subsequently, the electron beamlets 7 may enter the end module.Hereinafter, the term ‘beamlet’ refers to a modulated beamlet. Such amodulated beamlet effectively comprises time-wise sequential portions.Some of these sequential portions may have a lower intensity andpreferably have zero intensity—i.e. portions stopped at the beam stop.Some portions may have zero intensity in order to allow positioning ofthe beamlet to a starting position for a subsequent scanning period.

The end module 22 is preferably constructed as an insertable,replaceable unit, which comprises various components. In thisembodiment, the end module may comprise a beam stop array 10, a scanningdeflector array 11, and a projection lens arrangement 12, although notall of these need be included in the end module and they may be arrangeddifferently.

After passing the beamlet stop array 10, the modulated beamlets 7 maypass through a scanning deflector array 11 that provides for deflectionof each beamlet 7 in the X- and/or Y-direction, substantiallyperpendicular to the direction of the undeflected beamlets 7. In thisembodiment, the deflector array 11 may be a scanning electrostaticdeflector enabling the application of relatively small driving voltages.

Next, the beamlets may pass through projection lens arrangement 12 andmay be projected onto a target surface 24 of a target, typically awafer, in a target plane. For lithography applications, the targetusually comprises a wafer provided with a charged-particle sensitivelayer or resist layer. The projection lens arrangement 12 may focus thebeamlet, for example resulting in a geometric spot size of about 10 to30 nanometers in diameter. The projection lens arrangement 12 in such adesign for example provides a demagnification of about 100 to 500 times.In this preferred embodiment, the projection lens arrangement 12 isadvantageously located close to the target surface.

In some embodiments, a beam protector may be located between the targetsurface 24 and the focusing projection lens arrangement 12. The beamprotector may be a foil or a plate, provided with needed apertures, forabsorbing the resist particles released from the wafer before they canreach any of the sensitive elements in the lithography machine.Alternatively or additionally, the scanning deflection array 9 may beprovided between the projection lens arrangement 12 and the targetsurface 24.

Roughly speaking, the projection lens arrangement 12 focuses thebeamlets 7 to the target surface 24. Therewith, it further ensures thatthe spot size of a single pixel is correct. The scanning deflector 11may deflect the beamlets 7 over the target surface 24. Therewith, itneeds to ensure that the position of a pixel on the target surface 24 iscorrect on a microscale. Particularly, the operation of the scanningdeflector 11 needs to ensure that a pixel fits well into a grid ofpixels which ultimately constitutes the pattern on the target surface24. It will be understood that the macroscale positioning of the pixelon the target surface is suitably enabled by a wafer positioning systempresent below the target 24.

Such high-quality projection may be relevant to obtain a lithographymachine that provides a reproducible result. Commonly, the targetsurface 24 comprises a resist film on top of a substrate. Portions ofthe resist film may be chemically modified by application of thebeamlets of charged particles, i.e. electrons. As a result thereof, theirradiated portion of the film may be more or less soluble in adeveloper, resulting in a resist pattern on a wafer. The resist patternon the wafer may subsequently be transferred to an underlying layer,i.e. by implementation, etching and/or deposition steps as known in theart of semiconductor manufacturing. Evidently, if the irradiation is notuniform, the resist may not be developed in a uniform manner, leading tomistakes in the pattern. Moreover, many of such lithography machinesmake use of a plurality of beamlets. No difference in irradiation oughtto result from deflection steps.

FIG. 3 shows a conceptual diagram of an exemplary charged particlelithography system 1A, divided into three high level sub-systems: awafer positioning system 25, an electron optical column 20, and datapath 30. The wafer positioning system 25 moves the wafer 24 under theelectron optical column 20 in the x-direction. The wafer position system25 may be provided with synchronization signals from the data pathsub-system 30 to align the wafer with the electron beamlets generated bythe electron-optical column 20. The electron-optical column 20 mayinclude the charged particle multi-beamlet lithography machine 1 asshown in FIG. 2. Switching of the beamlet blanker array 9 may also becontrolled via the data path sub-system 30, using pattern bitmap data.

In FIGS. 4A-4D exemplary embodiments of a data path sub-system 30 areshown for a lithography system 301A-301D with control and datainterfaces forming the data path sub-system 30. The diagrams show ahierarchical arrangement with three interfaces, a cluster interface 303,cluster element interface 305, and the lithography subsystem interfaces307. Multiple lithography subsystems 316 are shown, each including acharged particle multi-beamlet lithography machine 1 such as shown inFIG. 2. It is possible that there is only on lithography subsystem 316.

Subsystems 316 include, for example, a wafer load subsystem (WLS), waferpositioning subsystem (WPS), an illumination optics subsystem (ILO) forgenerating electron beamlets, a pattern streaming subsystem (PSS) forstreaming beam switching data to the lithography element, a beamswitching subsystem (BSS) for switching the electron beamlets on andoff, a projection optics subsystem (POS) for projecting beamlets ontothe wafer, a beam measurement subsystem (BMS), and a metrology subsystem(MES).

Each subsystem 316 may operate independently and may include a memoryfor storing instructions and a computer processor for executing theinstructions. The memory and processor may be implemented in eachsubsystem as a plug-in client (PIC) 315. A suitable implementation of asubsystem may include, for example, a personal computer running theLinux operating system. The subsystems may include a hard disk ornon-volatile memory for storing their operating system so that eachsubsystems boots from this disk or memory. These and other featuresdiscussed below enable a design where each subsystem may be anautonomous unit which can be designed, built and tested as anindependent unit without needing to consider constraints imposed byother subsystems. For example, each subsystem may be designed withsufficient memory and processing capacity to properly perform thefunctions of the subsystem during its operating cycle, without needingto take into account the demands on memory and processing capacity madeby the other subsystems. This is particularly advantageous duringdevelopment and upgrade of the system, when these requirements are influx. With this design the total required memory and processing capacitymay be increased, and redundancy of these components may need to beimplemented within each subsystem. However, the simplified design maylead to faster development and simpler upgrade.

The subsystems 316 may be designed to receive commands via the controlnetwork 420 and may execute the commands independently from the othersubsystems, reporting results for the command execution and transferringany resulting execution data upon request.

The subsystems 316 may be designed as autonomous units, but designed toboot from a central disk or memory, for example on the data network hub.This reduces the reliability problem and cost of individual hard disksor non-volatile memory in each subsystem, and permits more easy softwareupgrade of a subsystem by updating the boot image for the subsystem inthe central location

The cluster interface 303 may comprise interfaces for communicationbetween a lithography cluster front-end 306 and one or more host systems302, and/or between the cluster front-end 306 and one or more operatorconsoles 304.

The cluster element interface 305 may comprise interfaces forcommunication between the cluster front-end 306 and a lithographyelement network comprising a element control unit 312 and/or a datanetwork hub 314. The element control unit 312 may be in communicationwith a data network hub 314 via link 406, wherein the communication ispreferably uni-directional from the element control unit 312 to the datanetwork hub 314.

The lithography subsystem interface 307 may comprise interfaces betweenthe element control unit 312 and the lithography subsystems 316, andbetween the data network hub 314 and the lithography subsystems 316. Thesubsystems 316 may communicate with the element control unit 312 viacontrol network 420, and the subsystems 316 may communicate with thedata network hub 314 via data network 421.

The operator interfaces and interfaces to higher-level host supervisoryand automation computers may be made not with the individual lithographyelements but at the cluster front-end 306.

Preferably the data path 320 directly connects pattern streamer 319 tothe subsystem(s) responsible for modulating or switching the chargedparticle beams. The pattern streamer 319 may stream pattern data to thelithography subsystems 316 to control the modulating and switching ofthe charged particle beams. The pattern data is typically streamed tothe relevant subsystems in a bit-map format, since the quantity of datais too great for local storage at the subsystem.

The subsystems 316 may be connected via a control network to a elementcontrol unit 312, also referred to as a Support Subsystem Control orSUSC. The element control unit 312 may comprise memory and a computerprocessor for controlling operation of the lithography subsystems 316.

In the examples of FIG. 4A and FIG. 4B the pattern data streamed fromthe pattern streamer 319 to the lithography subsystem 316 may includethe data for the common chip design part and the data for the uniquechip design part. In FIG. 4A the unique chip design part may be added tothe pattern data in the pattern data processing unit 318. In FIG. 4B theunique chip design part may be added to the pattern data in the patternstreamer 319.

In the examples of FIG. 4C and FIG. 4D the pattern data streamed fromthe pattern streamer 319 to the lithography subsystem 316 may includethe data for the common chip design part. In FIG. 4C the unique chipdesign part may be added to the pattern data by the lithographysubsystem 316 under control of the element control unit 312. In FIG. 4Dthe unique chip design part may be added to the pattern data by thelithography subsystem 316 under control of the host system 302.

In FIGS. 4A-4D the pattern streamer 319 may be controlled by the elementcontrol unit 312 via the control network 420. Furthermore, the patternstreamer 319 may be a part of the lithography subsystem 316.

FIG. 5 shows an exemplary functional flow diagram of an embodiment of adata path using real-line rasterization. In FIG. 3 the functional flowdiagram is split into four sections: 3010 is used to indicate a dataformat of underlying data outputs/inputs; 3020 shows the process flowincluding data outputs/inputs (parallelograms) and functional elements(rectangles); 3030 is used to indicate process steps performed atoverlying functional elements; and 3040 is used to indicate how oftenthe process steps are typically performed, e.g. once per design 3041,once per wafer 3042 or once per field 3043. Roman I, II and III indicatewhen the feature data set and/or the selection data may be provided tothe data path.

Input to the process may be GDS-II design layout data 2007, or a designlayout in any other suitable format such as an OASIS data format,defining the common chip design part. The pattern data processing system318 may preprocess 1022 the GDS-II file once per design, as indicated bythe arrow 3041 at the bottom.

Preferably the preprocessing 1022 does not involve the unique chipdesign part, enabling the pattern data preprocessing system 318 to belocated at a less secured environment. It is also desirable to minimizeexposure time of the unique chip design part for security reasons. Thesecurity aspect is important as the uniqueness of the chip willtypically be used for data security, traceability andanti-counterfeiting applications. The processes within the dashed block,i.e. from software processing 1071A until hardware processing 1073 aretypically performed at the lithography machine 1,1A enabling a moresecure operating environment. By inserting the unique chip design partat a later stage, the amount of time that the code is used within thelithography system 301A-301D can be minimized.

The unique chip design part may be inserted into the pattern data atvarious stages in the functional flow, indicated by roman I, II and III.

The unique chip design part may be inserted into the pattern data uponprocessing of the design layout data input, in this example GDSII input,indicated by roman I. At this stage the pattern data processing istypically performed in a vector based data format. As this operation istypically performed at the pattern data processing unit 318 located in aless secure environment, insertion of the unique chip design part atthis stage I is least preferred.

More preferably the insertion of the unique chip design part into thepattern data may be performed at the software processing stage 1071A asindicated by roman II, or at the streaming stage 1071B as indicated byroman III. The S/W processing stage 1071A is typically performed onceper wafer, as indicated by the second arrow 3042 from the bottom. Thestreaming stage 1071B is typically performed once per field or once perchip, as indicated by the third arrow 3043.

The S/W processing stage 1071A and the streaming stage 1071B may beimplemented at the pattern streamer 319. The hardware processing stage1073 on the right side of the functional flow typically involves theblanker being controlled by the pattern data 2009 including the commonchip design part and the unique chip design part.

The GDS-II format pattern data may undergo off-line processing 1022,typically including proximity effect correction, resist heatingcorrection, and/or smart boundaries (jointly depicted 3031). Theresulting corrected vector pattern data 2008 may be in a vector formatan may include dose information, depicted as 3011. This off-lineprocessing 1022 is usually performed once for a given pattern design,for one or more batches of wafers. In case of inserting the unique chipdesign part at this stage, indicated by roman I, the off-line processing1022 may need to be performed more frequently, up to once per wafer oreven once per field or chip.

Next, in-line processing of the vector tool input data 2008 may beperformed to rasterize the vector data 2008 to generate pattern systemstreamer (PSS) bitmap data 3021 in e.g. a 4-bit greyscale bitmap format3012.

This processing is typically performed in software. The unique chipdesign part may be added at this stage, as indicated by roman II. Thepattern streamer 319 may then processes the PSS format data 3021 togenerate blanker format data 2009, possibly including correctionsinvolving a full or partial pixel shift in the X and/or Y direction forbeam position calibration, field size adjustment, and/or field positionadjustment as before on the bitmap data, jointly depicted 3032.Alternatively to entry point II, the unique design part may be added atthis stage as indicated by roman III. This processing may be performedper field. The blanker format pattern data 2009 may then be transmitted3022 to the lithography system for exposure of the wafer.

As indicated in FIG. 5, rasterization may be performed at the streamingstage 1071B, which typically involves real-time processing performed inhardware. Corrections for beam position calibration, field sizeadjustment, and/or field position adjustment 3032 may be performed onvector format PSS format data 3021, and then rasterization may convertthis to a blanker format 2009. When the corrections are made on vectordata, both full pixel shifts and subpixel shifts in the X and Ydirection can be made.

The pre processing 1022 of the GDSII input 2007 is preferably performedsuch to enable insertion of the unique chip design part at a laterstage. Hereto bit space may be reserved within intermediate pattern dataor place holders may be added to intermediate vector format data wherethe unique chip design data is to be inserted at a later stage.Advantageously, besides the mentioned security advantage, this avoidsthe need to regenerate huge amounts of pattern data before each exposureof the wafer for each unique chip, which would require very high CPUpower and very large amounts of memory.

In FIGS. 4A-4D communication 402 between the cluster front-end 306 andSUSC 312 may be designed for transfer of process programs (PPs) to theSUSC 312. A protocol based on JavaScript Object Notation (JSON) may beused for this purpose. The protocol preferably provides an instructionfor creation of process jobs (PJs), transferring the PP file and anyassociated parameters, to instruct the SUSC 312 to create a PJ based onthe PP. Additional commands may include Abort and Cancel instructions.

Communication from the SUSC 312 to the cluster front-end 306 may includeacknowledgment messages, progress reporting, and error and alarmmessages.

Communication 401 between the SUSC 312 and lithography subsystems 316across control network 420 is preferably strictly controlled using onlythe element control unit protocol to ensure a quasi real-timeperformance in the network. Communication 405 between SUSD 314 andcluster front-end 306 may be designed for retrieval of PJ results, jobtracing and data logging from the SUSD 314. A Hyper-Text TransferProtocol (HTTP) may be used for this communication link.

Communication 403 between the lithography subsystems 316 and SUSD 314may be designed for one-way collection of data from the subsystems 316.The data may be communicated using a variety of protocols, such assyslog, HDF5, UDP and others.

High volume data may be sent using a User Datagram Protocol (UDP) tosend data without the large overhead of handshaking, error checking andcorrection. Due to the resulting very low transmission overhead, thedata may thus be regarded as being received in real-time.

The hierarchical data format HDF5 may be used for transmission andstorage of the high-frequency data. HDF5 is well suited to storing andorganizing large amounts of numerical data, but is usually not used in aUDP environment. Other data formats such as CSV or TCP can also be used,particularly for low level (low volume) data.

The operation of the lithography subsystems 316 may be controlled usingthe PP, which may comprise a sequence of actions to be performed. Theelement control unit 312 may be loaded with a PP, and may schedule andexecute the PP as requested by a host system 302 or an operator thoughan operator console 304.

Process programs (PP) and process jobs (PJ) may be based on the SEMIstandard, e.g. SEMI E30: “Generic Model for Communications and Controlof Manufacturing Equipment (GEM)”, SEMI E40: “Standard for ProcessingManagement”, SEMI E42: “Recipe Management Standard: Concepts, Behavior,and Message Services”, and/or SEMI E139: “Specification for Recipe andParameter Management (RaP)”. The PP may take the role of a recipe, e.g.as defined in the SEMI E40 standard. Although the SEMI standards specifymany requirements on how to deal with recipes, the standards may becontradictory so that recipes are preferably avoided. Instead, editableand unformatted PP may be used in the form of so-called Binary LargeObjects (BLOBs).

The PP may be a pre-planned and reusable portion of the set ofinstructions, settings and parameters that determine the processingenvironment of the wafer and that may be subject to change between runsor processing cycles. PPs may be designed by the lithography tooldesigners or generated by tooling.

PPs may be uploaded to the lithography system by the user. PPs may beused to create PJs. A PJ may specify the processing to be applied to awafer or set of wafers by a lithography subsystem 316. A PJ may definewhich PP to use when processing a specified set of wafers and mayinclude parameters from the PP (and optionally from the user). A PJ maybe a system activity started by a user or host system.

PPs may be used not only for controlling the processing of wafers, butalso for service actions, calibration functions, lithography elementtesting, modifying element settings, updating and/or upgrading software.Preferably no subsystem behavior occurs other than what is prescribed ina PP, with the exception of certain allowed additional categories, suchas automatic initialization during power-up of a module or subsystem,periodic and unconditional behavior of a subsystem, as far as thosedon't influence PJ execution, and the response to an unexpectedpower-off, emergency or EMO activation.

A PP may be divided into steps. Most steps comprise a command andidentify a subsystem which is to perform the command. The step may alsoinclude parameters to be used in performing the command, and parameterconstraints. The PP may also include scheduling parameters to indicatewhen a step is to be performed, e.g. to be performed in parallel, insequence, or synchronized.

To execute a command step of the PJ, the element control unit 312 maysend the command indicated in the PJ to the subsystem indicated in therelevant step of the PJ. The element control unit 312 may monitor timingand may receive the results from the subsystem.

In the example of FIG. 4A the pattern data processing system 318 may beconfigured to receive unique chip design data 430 from a unique datagenerator 330 and to insert the unique chip design data into the patterndata.

In the example of FIG. 4B the pattern streamer 319 may be configured toreceive unique chip design data 430 from a unique data generator 330 andto insert the unique chip design data into the pattern data.

In the example of FIG. 4C the element control unit 312 may be configuredto receive unique chip design data 430 from a unique data generator 330and to control insertion of the unique chip design data into the patterndata. The unique chip design data may be transmitted to a lithographysubsystem 316 with a process job.

In the example of FIG. 4D the host system 302 may be configured toreceive unique chip design data 430 from a unique data generator 330 andto control insertion of the unique chip design data into the patterndata. The unique chip design data may be transmitted to a lithographysubsystem 316 with a process job.

Generally, the unique chip design data 430 may be in a format thatenables direct insertion into the pattern data. Alternatively the uniquechip design data 430 comprises information that enables the data to begenerated that is to be inserted into pattern data.

The unique chip design data 430 may be generated by the unique datagenerator 330 based on secret data 440 received from an externalprovider 340. Alternatively the secret data may be generated within theunique data generator 330. The secret data 440 may be encrypted anddecryptable by the unique data generator 330. The secret data 440 mayinclude secret keys and/or secret IDs.

The unique data generator 330 may be realized as a black box device. Theunique chip design data 430 may be generated by the back box device. Theblack box device may be a source external to the maskless lithographicexposure system and is preferably located within a manufacturing part ofthe fab. The black box may be owned by a third party, e.g. an IP blockowner or the owner of the manufactured chip, or a key managementinfrastructure owner. Advantageously the black box can be located withinthe fab close to the operations of the lithography machine, therebyminimizing public exposure of the unique chip design data. This incontrast to known chip manufacturing solutions, where a black box forindividualizing chips is typically located outside of the fab and usedto individualize the chips after being created.

A black box device may include an ID/key manager and a unique datagenerator 330 that cooperate in the creation of the unique chip designdata 430. The ID/key manager may receive product ID/serial numberinformation from a manufacturing database and batches of ID/key pairsfrom a key management service possibly located outside of the masklesslithographic exposure system. The product ID/serial number informationand the batches of ID/key pairs may be used to control the generation ofthe unique chip design data 430. Furthermore, the product ID/serialnumber information may be used to track the chips through the creationprocess to be able the chips to be matched with their ID/serial numbersafter being created. Alternatively or additionally, the productID/serial number information may be used to include the ID/serial numberin or on the chip by a not shown but known per se process.

FIG. 6 shows a process of creating a unique chip according to anexemplary embodiment of the invention. In this embodiment the identicalpart of the chip may be created using photolithography (using a mask)and the individualized (unique) part of the chip may be created usingcharged particle multi-beamlet lithography (without a mask). Mask-basedphotolithography is the conventional method for making chips, and at thepresent time enables low cost and high throughput production usingconventional lithography equipment already in service at a typical fab.However, using mask-based lithography for making unique chips isimpractical because this would require a large number of (expensive)masks, each having a different pattern. Maskless lithography using e.g.a charged particle multi-beamlet lithography system is a newly developedtechnology which has not yet been commercialized widely and still cannotachieve the same high throughput of mask-based systems.

Using a combination of mask-based and maskless lithography enables lowcost and high throughput production of unique chips. Various methods maybe used for combining mask-based and maskless lithography to create theunique chips. Some examples are discussed with reference to FIGS. 6-8below. These examples illustrate processes for fabricating a uniquepattern of conducting vias for interconnecting two conducting layers ofthe chip. However, the portion of the chips which is individualized tocreate the unique chips may be layers other than a via layer. Forexample, a semiconductor layer may be individualized by creating aunique arrangement of transistors and diodes in each chip by varying thedoping of active regions of the transistors or diodes. This variation indoping is very hard to detect even when shaving the chip and analyzingeach layer, since the variation in amount of dopant in the semiconductorlayer is difficult to detect, making the chip very difficult to reverseengineer. In other examples, a contact layer may be individualized byforming a unique arrangement of connections between a metal layer and agate, or a metal layer may be individualized by forming a uniquearrangement of connections between circuit elements, or these examplesmay be used in combination of other features of the circuit may beselectively formed in a unique combination for each chip to realize theunique chips.

At the beginning of the process of FIG. 6 the wafer may comprise abottom metal layer 201 which has been previously patterned to formconductive connecting lines and an insulating layer 202 (for exampleSiO2) with resist 205 (e.g. KrF resist) on top as shown in FIG. 6A.

For the creation of the identical part (e.g. common part 101), theresist 205 may undergo a mask-based exposure, e.g. using a KrF laser,followed by a development step wherein patterns defined by the mask areremoved from the resist layer 205, as shown in FIG. 6B. In an etchingand stripping step these patterns may be etched into the insulatinglayer 202 and the resist is then removed, as shown in FIG. 6C.

Next, a conductive layer 207 may be applied onto the etched and strippedinsulating layer, as shown in FIG. 6D. For example a chemical vapordeposition with Tungsten (CVD-W) may be used, as shown in FIG. 6D.Chemical-mechanical planarization (CMP) may be used to removesuperfluous conductive material resulting in the wafer having the bottommetal layer 201 and a layer 202 comprising insulating material withconductive material present in the locations where conductive vias aredesired, as defined by the mask exposure, shown in FIG. 6E.

Next, for the creation of the unique part 102, the wafer may receive oneor more etch barrier films for etching the insulating layer 202. Forexample, a spin on carbon (SOC) film 203 and a silicon-containingantireflective coating (SiARC) hard mask 204, with an e-beam resist 206formed on top, covering the insulating layer 202 including the etchedpart from the mask-based photolithography phase, as shown in FIG. 6F.The resist 206 may undergo a maskless e-beam exposure followed by adevelopment step wherein patterns exposed by the e-beams are removedfrom the resist 206, as shown in FIG. 6G. In an etching and strippingstep these patterns may be etched into the etch barrier films 203 and204, and the resist may be removed, as shown in FIG. 6H. Next, thepatterns that are created in etch barrier films 203, 204 may be etchedinto the insulating layer 202, and films 203, 204 may be stripped, asshown in FIG. 6I.

Next, a conductive layer 207 may be applied onto the etched and strippedinsulating layer 202, as shown in FIG. 6J. For example a chemical vapordeposition with Tungsten (CVD-W) may be used. Chemical-mechanicalplanarization (CMP) may remove superfluous conductive material, as shownin FIG. 6K, resulting in the wafer having a bottom metal layer 201 and alayer 202 comprising insulating material with conductive materialpresent in the locations where conductive vias are desired, as definedby the mask exposure and the maskless exposure, as shown in FIG. 6K. Thelocations for the conductive vias defined by the mask exposure will bethe same for every chip of the set of chips made using the same mask.However, the locations for the conductive vias defined by the masklessexposure may be different for every chip of the set of chips, so thatevery chip of the set has a unique set of vias.

Following the process of FIG. 6, an upper metal layer may be depositedover insulating layer 202 and patterned to create a second set ofconductive connecting lines, so that the vias formed in insulating layer202 function as electrical connections between the bottom metal layer201 and the upper metal layer. Since each chip of the set of chips has aunique arrangement of vias, each chip can be designed to have a uniqueelectrical circuit.

In the embodiment of FIG. 6 two CMP steps may be needed. Dishing anddouble erosion effects caused by the CMP steps can affect the thicknessof the insulating layer including the conductive material of the vias.This can have a negative impact on analogue and radio frequencyperformance of the chip. FIG. 7 shows an improved process for creatingunique chips wherein only a single CMP step may be needed.

FIG. 7 shows a process of creating a unique chip according to anotherexemplary embodiment of the invention. In this embodiment the identicalpart (e.g. common part 101) of the chip may be created using mask-basedphotolithography and the individualized part (e.g. unique part 102) ofthe chip may be created using maskless charged particle multi-beamletlithography.

At the beginning of the process of FIG. 7 the wafer may comprise abottom metal layer 201 which has been previously patterned to formconductive connecting lines, and an insulating layer 202 (for exampleSiO2), under etch barrier films 203 and 204 (e.g. SOC+SiARC HM) and aresist 205 (e.g. KrF resist), as shown in FIG. 7A. Advantageously, theetch barrier films 203 and 204 may be used for both the mask-basedphotolithography and the maskless charged particle multi-beamletlithography phase, thereby eliminating the need for a CMP step in thephotolithography phase, as will be further explained below.

For the creation of the identical part, the resist 205 may undergo amask exposure, e.g. using KrF laser, followed by a development stepwherein patterns defined by the mask may be removed from the resist 205,as shown in FIG. 7B. In an etching and stripping step these patterns maybe etched into the SOC 204 and the resist is removed, as shown in FIG.7C.

Next, for the creation of the unique part, the wafer may receive ane-beam resist 206, covering the etch barrier films 203 and 204 includingthe etched part from the photolithography phase, as shown in FIG. 7D.The resist 206 may undergo an e-beam exposure followed by a developmentstep wherein patterns defined by the e-beams may be removed from theresist 206, as shown in FIG. 7E. In an etching and stripping step thesepatterns may be etched into the etch barrier films 203, 204 and theresist 206 is removed, as shown in FIG. 7F. Next, the patterns createdin the etch barrier films 203, 204 in both the mask-basedphotolithography phase and the maskless charged particle multi-beamletlithography phase may be etched into the insulating layer 202, and thefilms 203, 204 may be stripped as shown in FIG. 7G.

Next, a conductive layer 207 may be applied onto the etched and strippedinsulating layer 202 for both the identical part and the unique part ofthe chip, as shown in FIG. 7H. For example a chemical vapor depositionwith Tungsten (CVD-W) may be used. Chemical-mechanical planarization(CMP) may remove superfluous conductive material resulting in the waferhaving the bottom metal layer 201 and a layer 202 comprising insulatingmaterial with conductive material at locations defined by the maskexposure and the maskless exposure, as shown in FIG. 7I.

As described with reference to FIG. 6, an upper metal layer may bedeposited over insulating layer 202 and patterned to create a second setof conductive connecting lines, so that the vias formed in insulatinglayer 202 function as electrical connections between the bottom andupper metal layers. Since each chip of the set of chips has a uniquearrangement of vias, each chip can be generated having a uniqueelectrical circuit.

FIG. 8 shows a process of creating a unique chip according to anotherexemplary embodiment of the invention. In this embodiment, all or aportion of the identical part (e.g. common part 101) of the chip as wellas the unique part 102 of the chip may be created using maskless chargedparticle multi-beamlet lithography.

At the beginning of the process of FIG. 8 the wafer may comprise abottom metal layer 201 which has been previously patterned to formconductive connecting lines, and an insulating layer 202 (for exampleSiO2), under etch barrier films 203 and 204 (e.g. SOC+SiARC HM) and ane-beam resist 206 (e.g. KrF resist), as shown in FIG. 8A.

The resist 206 may undergo an e-beam exposure followed by a developmentstep wherein patterns defined by the e-beams may be removed from theresist layer 206, as shown in FIG. 8B. In an etching and stripping stepthese patterns may be etched into the etch barrier films 203, 204 andthe resist 206 may be removed, as shown in FIG. 8C. Subsequently thepatterns may be etched into the insulating layer 202, and the etchbarrier films 203, 204 are stripped, as shown in FIG. 8D.

Next, a conductive layer 207 may be applied onto the etched and strippedinsulating layer 202 for both the identical part and the unique part ofthe chip, as shown in FIG. 8E. For example a chemical vapor depositionwith Tungsten (CVD-W) may be used. Chemical-mechanical planarization(CMP) may remove superfluous conductive material resulting in the waferhaving the bottom metal layer 201, and a layer comprising insulatingmaterial with conductive material formed at locations as defined by thee-beams, as shown in FIG. 8F.

An advantageous method for combining the use of mask-based lithographyand maskless lithography for the production of unique chips is toarrange the individualized portion of the chips on a single layer of thechip, e.g. on a single via layer, contact layer, other metal layer, orsemiconductor layer. The entire layer containing the individualizedstructures (e.g. vias, contacts, connecting lines, transistors etc.) maythen be exposed using maskless/e-beam lithography, while all of theother layers are exposed using conventional mask-based photolithography.

This is illustrated in the embodiment shown in FIG. 9 showing variouslayers of a unique chip. In this example, the chip can be considered tohave common parts 101 and a unique part 102 in different areas of thechip. These parts 101, 102 are formed of multiple layers, and thestructures (such as interconnecting lines, vias, terminals oftransistors and diodes, active regions of transistors and diodes etc.)formed in the common parts 101, 102 may form electrical circuits such aslogic circuits and data storage (memory) circuits or data storagestructures. The structures formed in the common parts 101 are commonstructures which are the same in every chip of the set of chips. Thecommon structures of the common parts 101 are indicated in FIG. 9 as 201a, 202 a, 208 a, 209 a, 201 c, 202 c, 208 c and 209 c. The structuresformed in the unique (non-common) part 102 may be a mix of commonstructures which are the same in every chip of the set of chips(indicated in FIG. 9 as 201 b, 208 b and 209 b) and non-commonstructures which are unique for each chip (indicated in FIG. 9 as 202b).

In this example, layers 201, 208 and 209 are exposed using mask-basedlithography and are designed to be identical for every chip of the set,i.e. these layers include common structures (201 a-c, 208 a-c and 209a-c) which are identical for all chips of a set of chips. The electricalcircuits formed by these common structures are thus identical in everychip.

Layer 202 is exposed using maskless lithography and is different foreach chip of the set of chips. Note that the portions of layer 202within the common part 101 contains common structures (202 a and 202 c)which are identical for every chip, while the portions of layer 202within the unique part 102 contain non-common structures (202 b) whichare unique for each chip. In this way, a unique circuit (also referredto as a non-common circuit) for each chip can be created in the uniquepart 102. For example, the chip may have transistors, diodes andconnecting lines which are identical for every chip but a uniquearrangement of conducting vias in layer 202 which results in forming aunique circuit in the unique part 102 for each chip.

Note that the individualized portion of the chips may also be formed ontwo or more layers of the chip which are exposed using masklesslithography, while the remaining layers are exposed using mask-basedlithography.

The layer of the chip which contains the individualized structures, e.g.the non-common structures 202 b of FIG. 9, preferably has one or moreother layers formed above the individualized layer, and may have one ormore other layers formed below the individualized layer. This makes itmore difficult to determine the structures of the individualized portionof the chip by non-destructive inspection, particularly where there areseveral layers above the individualized layer and/or the overlyinglayers include structures or materials which are difficult to penetrateduring inspection. This also applies when the individualized structuresare formed on more than one layer, so that at least one of theindividualized layers preferably has one or more overlying layers andmay have one or more other layers below.

The embodiments of FIGS. 6-8 are described above using the example ofindividualized part of the chip comprising a unique arrangement ofconducting vias formed using maskless lithography. The structure of theunique chips may be further improved by merging adjacent conducting viasproduced using the maskless lithography process to effectively form alarger single via, as depicted in the example shown in FIG. 12A-D. FIG.12A shows a side view and FIG. 12B shows a top view of multiple roundvias 217 a, 217 b formed using a conventional mask-basedphotolithography process, to form an electrical connection between twometal layers 211 a, 211 b. Due to the limitations of the optical systemsused in conventional photolithography, the merging of these vias into asingle larger oblong via is difficult to achieve in practice. Using amaskless charged particle lithography system, these constraints are notpresent and a larger oblong single via can be 217 e produced connectingmetal layers 211 a, 211 b, e.g. by exposing two vias 217 c, 217 d closetogether so that they merge to form a double via, as shown in FIGS. 12Cand 12D showing side and top views respectively. This double via enablesa more reliable connection to be made between the two metal layers,which may conduct more current, and yields a further improvement in theunique chip.

In the embodiments of FIG. 6 and FIG. 7 the unique part of the chip orthe layer(s) containing the individualized features/structures may begenerated based on pattern data including a common chip design part anda unique chip design part, as discussed in conjunction with FIGS. 4A-5.The size of the common chip design part may depend on the size of theidentical part of the chip created using photolithography. When a largeportion of the identical part is exposed using photolithography, thecommon chip design part in the pattern data may be small. It is possiblethat the pattern data only includes a unique chip design part in casethe unique part of the chip only or mostly has unique features.

In the embodiment of FIG. 8 the pattern data may include a common chipdesign part that is used to create the identical part of the chip and aunique chip design part that is used to create the unique part of thechip, as discussed in conjunction with FIGS. 4A-5. In the embodiment ofFIG. 9 the pattern data may include a common chip design part that isused to create the identical part of the individualized layer and aunique chip design part that is used to create the unique part of theindividualized layer, as discussed in conjunction with FIGS. 4A-5.

A predetermined value, such as a serial number or any other kind ofidentification code may be embedded in a chip using a masklesslithography exposure system, such that it becomes readable from the chipelectronically, optically or magnetically by automated means. In thefollowing examples a serial number is used as non-limiting example of apredetermined value.

FIG. 10 shows an embodiment of a unique chip comprising a unique chiphaving multiple layers and including a common part 101 and a unique part102, which may be formed using any of the methods described above. Inthis example, the unique part comprises a first portion 102 a and asecond portion 102 b on a layer 102, where the first portion 102 astores a predetermined value which is uniquely associated with thesecond portion 102 b.

In one embodiment, the first portion 102 a forms a mask ROM which storesa serial number and the second portion forms a circuit which generates apredetermined output value when provided with a predetermined inputvalue, where the output value is different for every chip of the set ofchips when provided with the same input value, or where each chip of theset of chips generates a unique combination of output value to inputvalue. The serial number stored in the first portion 102 a is uniquelyassociated with the circuit formed by the second portion 102 b. Theserial number may be readable from an output of the chip, so that theunique chip can be identified by reading the serial number. An inputvalue may be provided to the circuit of the chip and the resultingoutput value generated by the circuit may be read from the chip. Thenthe serial number and the output value read from the chip may beevaluated to securely determine the identity of other information aboutthe chip.

An electronically readable serial number may be read from the chip e.g.via one or more ports or pins connected a chip's electronic circuit orwirelessly e.g. using a NFC or Bluetooth interface connected to thechip's electronic circuit. An optically readable serial number may bewritten on a metal layer of the chip. The shape of the metal layer maybe used to encode the serial number, e.g. in the form of a small barcode or QR code, or an optically identifiable set of metal lines, vias,or circuitry. FIG. 11 shows a top view of a layer of an exemplarysemiconductor chip 100 having a shape which stores a serial number in aunique portion 102 c, in this example in the form of a QR code which maybe optically readable. The portion 102 c with the QR code may form partof a first portion 102 a as shown in FIG. 10, or part of a circuitformed by a second portion 102 b as shown in FIG. 10. Such a readableserial number may be read using an optical reader scanning the surfaceof the chip, possibly thereby penetrating one or more of the upperlayers of the chip to access the serial number on an embedded chiplayer. An optically readable serial number that is written on a chiplayer that is covered by one or more other chip layers may be read usinga reader that can penetrate the chip, such as an electron microscope orx-ray machine.

Multiple serial numbers or identification codes may be embedded in achip. Multiple serial numbers may be written on the same chip layer,e.g. the same metal layer, or on different chip layers. It is possiblethat one or more serial numbers can be read electronically from the chipwhile on or more other serial numbers can be read optically from thechip. The multiple serial numbers may be different serial numbers,copies of the same serial number in a same format or copies of the sameserial numbers in different formats. Non limiting examples of formatsare: sizes; ways of representing the serial number; encrypted andunencrypted forms of the same serial number.

The serial number may be used to create a unique association between theunique chip and software code. The software code may be accessible orusable only with the correct or verifiable serial number in the uniquechip. Preferably, the software code is embedded in the chip, e.g. in ROMcreated with the same maskless lithography exposure system as used forembedding the serial number. The software code may be external to thechip.

The serial number may be used in an authorization process that is tiedto a challenge-response circuitry embedded in the chip, preferablycreated using the same maskless lithography exposure system as used forembedding the serial number. The serial number may be read from the chipand used to obtain a challenge and response pair e.g. from a database.This response is the expected response to the challenge and should besecurely stored. This challenge and response pair may be predefined andtied to the serial number upon fabrication of the chip using themaskless lithography exposure system. Sending the challenge to the chipmay trigger the challenge-response circuitry to output a response, whichmay be compared with the expected response. In case of matchingresponses, the chip or a device or software using the chip may beauthorized or authenticated. Any known remedies againstman-in-the-middle attacks when communicating the serial number, thechallenge and the response to and from the chip may be additionallyapplied.

The predetermined value may be a public key or a private key used in apublic-private key encryption scheme. Both a public key and a privatekey may be stored in the chip for use in the public-private keyencryption scheme. The public and/or private key may be derivable fromone or more embedded predetermined values using an embeddedcryptographic or other mathematical function embedded in the chip.Preferably the embedded function has been created using the samemaskless lithography exposure system as used for creating thepredetermined value(s). The private key may be embedded within adecryption circuit that has been created in the chip using the samemaskless lithography exposure system as used for creating thepredetermined value(s).

The serial number may be used to enable parts of embedded functionalityor software in the chip. The embedded functionality or software may becreated using the same maskless lithography exposure system as used forcreating the serial number. Different parts of the embeddedfunctionality or software may be active depending on the serial number.There may be a unique relationship between the serial number and thepart to be activated. Alternatively, a range of serial numbers may betied to a part to be activated. The serial number may be used inconjunction with a uniquely encrypted vector for enabling functionalityof the chip depending on the uniquely encrypted vector. For example, apassport chip may be created wherein software is embedded for use inmultiple countries, and wherein software for only one country is to beactivated depending on the serial number. Thus, chips with MROMcontaining software for multiple countries can be created, wherein theserial number is used for activating the relevant software portions fora specific country.

The chip with an embedded serial number may be used in conjunction witha computer memory, wherein the computer memory is encrypted using theserial number. The memory without the chip may be undecryptable andtherefore inaccessible. Exchanging the chip with another chip may resultin the memory becoming undecryptable and therefore inaccessible.

The chip may be used as a ROM mask for data personalization.Personalized, possibly unique data may thus be written onto the chipwithout the need for expensive non-volatile memory.

1. An electronic device comprising a semiconductor chip which comprisesa plurality of structures formed in the semiconductor chip: wherein thesemiconductor chip is a member of a set of semiconductor chips, whereinthe set of semiconductor chips comprises a plurality of subsets ofsemiconductor chips, and the semiconductor chip is a member of only oneof the subsets; wherein the plurality of structures of the semiconductorchip includes a set of common structures which is the same for all ofthe semiconductor chips of the set, and a set of non-common structures,wherein the non-common structures of the semiconductor chip of thesubset are different from the non-common structures of the semiconductorchips in every other subset; wherein at least a first portion of thenon-common structures is adapted to store or generate a firstpredetermined value; wherein the first predetermined value is readablefrom outside the semiconductor chip by automated reading means.
 2. Theelectronic device according to claim 1, wherein the first predeterminedvalue is readable from outside the semiconductor chip by automatedelectromagnetic, optical, or electronic reading means.
 3. The electronicdevice according to claim 1, wherein the first predetermined value isreadable from the structure of the first portion of the non-commonstructures and/or wherein the shape of the first portion of thenon-common structures stores the first predetermined value.
 4. Theelectronic device according to claim 1, wherein a first non-commoncircuit is formed from the first portion of the non-common structures ofthe semiconductor chip and a first portion of the common structures ofthe semiconductor chip, and wherein the circuit configuration of thefirst non-common circuit of the semiconductor chips of each subset isdifferent from a circuit configuration of any of the semiconductor chipsin every other subset.
 5. The electronic device according to claim 1,wherein the first non-common circuit comprises at least one of: aread-only memory circuit which is fabricated with the firstpredetermined value pre-stored in the read-only memory circuit; a logiccircuit, wherein the logic circuit is adapted to generate the firstpredetermined value.
 6. The electronic device according to claim 1wherein the set of non-common structures of the semiconductor chip isdifferent from the set of non-common structures of every othersemiconductor chip of the set of the semiconductor chips.
 7. Theelectronic device according to claim 1, wherein the electronic devicecomprises at least one input terminal and at least one output terminal,and the first non-common circuit is connected to the input and outputterminals, and wherein first predetermined value is electronicallyreadable from the output terminal.
 8. The electronic device according toclaim 1, wherein the electronic device comprises at least one inputterminal for receiving a challenge and at least one output terminal foroutputting a response, and the first non-common circuit forms achallenge-response circuit connected to the at least one input terminaland the at least one output terminal, wherein the challenge-responsecircuit is adapted for generating a response at the at least one outputterminal based on a challenge applied to the at least one inputterminal, the challenge and the response having a predeterminedrelationship.
 9. The electronic device according to claim 8, wherein theresponse generated by the challenge-response circuit depends on both thechallenge applied to the at least one input terminal and the firstpredetermined value.
 10. The electronic device according to claim 1,wherein the plurality of structures are formed on three or more layersof the semiconductor chip, including one or more non-common layerscontaining the non-common structures, and at least one common layerabove the one or more non-common layers, the at least one common layercontaining common structures but no non-common structures.
 11. Theelectronic device according to claim 10, wherein all of the non-commonstructures are formed in only one layer of the semiconductor chip. 12.The electronic device according to claim 10, wherein the semiconductorchip comprises at least a second common layer below the one or morecommon layers, the second common layer containing common structures butno non-common structures.
 13. The electronic device according to claim1, wherein the plurality of structures are formed in a plurality oflayers of the semiconductor chip, and the non-common structures includeat least one of: connections between metal layers of the plurality oflayers; connections between a metal layer and a gate in a contact layerof the plurality of layers; connections in a local interconnect layer ofthe plurality of layers; and a P- or N-doped diffusion region of atransistor or diode of one of the plurality of layers.
 14. Theelectronic device according to claim 10, wherein the non-commonstructures of the one or more common layers are formed using a chargedparticle multi-beamlet lithography system, and the common layers areformed using a mask-based lithography process.
 15. The electronic deviceaccording to claim 1, wherein the set of semiconductor chips are allformed from a single wafer.
 16. A system for authentication between aplurality of remote terminals and a host system based on achallenge-response procedure, wherein each of the remote terminalscomprises an electronic device according to claim
 1. 17. A remoteterminal adapted for use in a system according to claim
 16. 18. A methodfor authentication in a system according to claim 16, the methodcomprising distributing the remote terminals to a plurality of users,sending a challenge from the host system to one of the remote terminals,receiving a response from the remote terminal, and authenticating theremote terminal if the response has to predetermined relationship withthe challenge.
 19. A method of manufacturing an electronic deviceaccording to claim 1, wherein at least a portion of the non-commonstructures are formed using a maskless lithographic exposure system. 20.The method of manufacturing an electronic device according to claim 19,wherein at least the first portion of the common structures are formedusing a mask-based photolithography system and the first portion of thenon-common structures are formed using a maskless lithographic exposuresystem.
 21. The method of manufacturing an electronic device accordingto claim 19, wherein pattern data used to control the masklesslithographic exposure system for forming the semiconductor chip includesa common chip design part representing the common structures and anon-common chip design part representing the non-common structures. 22.The method of manufacturing an electronic device according to claim 21,wherein the pattern data is based in part on secret data provided to themaskless lithographic exposure system during creation of a non-commondesign layout part.
 23. The method of manufacturing an electronic deviceaccording to claim 21, wherein the secret data originates from a uniquedata generator such as a black box device.